Secret Doors

Textures: whatever your wall texture is

What to 
do:  
	Make a hole in the wall where you want your door to be.  It should
be a bit smaller than a normal door...maybe 80 units high and 32 wide.
Next, make a brush that fits inside this hole, this will be your door,
and assign its texture as the same one as the rest of your wall.  Assign
this brush the "func_door_secret" entity, and then set your direction.
Give it a "sound" of "3", this is the most common setting.  Give it a 
"lip" of "1", this will make it retract first.  Set the "speed" to "60"
or so.